FIG. 7 is a schematic view of a conventional gas chromatograph. Reference numeral 2 denotes a glass insert of a sample introduction unit, and the distal end of the glass insert 2 is connected to one end of a capillary column 6. The other end of the capillary column 6 is connected to a detector 8. A carrier gas introduction tube 10 is connected to the proximal end portion of the sample introduction unit to supply a carrier gas whose pressure has been regulated.
A septum purge flow channel 12 for discharging part of a carrier gas is also provided at the proximal end portion of the sample introduction unit. The proximal end portion of the sample introduction unit is sealed with a septum 14. A needle extending from a sample injector is allowed to penetrate the septum 14 in such a manner that the distal end of the needle is inserted into the inside of the glass insert 2, and then a liquid sample is injected into the glass insert 2.
The outer circumferential portion of the glass insert 2 is covered with a heating block 51, and glass wool 53 held by a graphite ferrule 55 is placed inside the glass insert 2. A liquid sample is injected from the upper side of the glass insert 2 into the glass insert 2 through a needle. The liquid sample is allowed to flow downward together with a carrier gas, and is then brought into contact with the glass wool 53. The glass wool 53 is previously heated to about 250° C. by the heating block 51, and therefore the liquid sample flowing through the glass wool is heated as well as mixed and is then vaporized. The vaporized sample is split into two and introduced into both the capillary column 6 and a split flow channel 11. The sample flowing through the capillary column 6 is separated into its components, and the sample components are detected by the detector 8.
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